WAVIQ (Webcam Audio Visualizer In Quartz) is an Apple Quartz Composer based Audio Visualizer that combines input from the microphone and Webcam to form dynamic visualization. It is intended to be projected at concerts or used by VJs.

FreeForth is a small and fast interactive compiler composed of an
extensible set of macros generating inline compact i386 native code,
including floating-point instructions, and an easy interface to
Linux and Windows dynamic libraries. It uses two stacks to pass
subroutines arguments and results separately from return addresses, like
other Forth dialects, but unlike them, it is a simpler pure compiler
(without an interpreter) offering interactivity through "anonymous"
subroutines which are executed by their closing ";" macro. FreeForth is
fully documented by 100K of interactive online help. Since its first
release in 2006, it has been used every day for cross-development
of realtime industrial applications embedded in microcontrollers,
and for PC-controlled manufacturing test benches. The FreeForth
distribution includes an interactive incremental assembler for the
MSP430 microcontroller family.

Cacophony is a tool for creating and viewing interactive videos, especially music videos, using HTML5 video and canvas elements and Javascript. Interactive elements include visuals/story adapting in response to user input as text, mouse movement, drawings, and choices (choose-your-own-adventure). Input from the viewer can affect the subsequent video, and also be sent to a server for integration with other Web applications (social networking, sharing, and geotagging), which is possible because effects are rendered on-the-fly in the browser, not pre-rendered like traditional video. Input can also come from external sources (RSS and JSON), so you can integrate external data, or previously generated data, back into subsequent views of the video.

AnyMap is a flexible Flash-based solution for easily displaying any sort of data dealing with geographical locations. It contains maps of the US, the world, and US counties. It is driven by an XML interface and is easily implemented. There is no need for ActiveX on the server. Graphics are rendered on the client. All scripting languages (including ASP, PHP, ColdFusion, and Perl) are supported. You can easily add your own custom images and texts.

pulseaudio-mixer-cli is an interactive ncurses UI to control the volume of PulseAudio streams. It is somewhat like alsamixer, but focused not on sink volume levels (which can actually be controlled via alsamixer, with the alsa-pulse plugin), but rather on the volume of individual streams from applications, allowing the user to balance sound levels between them. Interaction with pulseaudio is done through the DBus interface, and the UI is designed to be as simple as possible, without heavy DE dependencies like GNOME libs or KDE/QT.

Swallowapps provides interactive tools for the design of Web (HTML5) content. You create the visual part of your application using visual tools and get instant feedback while you adjust dimensions, transformation matrices, colors, shadows, gradients, and other styling elements in an intuitive and interactive way. When the time comes for programming, Swallowapps combines the convenience of the commonJS packaging specification (the require() function, package.json, etc.) with an automatic build process. Modify any source module of any package which you use, hit F5 in the browser, and your updated application is reloaded. Swallowapps tools are built with themselves, so as you learn how to use the tools, you also learn how to modify them and make them tightly fit your specific needs.